Broadband, large scale acoustic energy harvesting via synthesized electrical load: II. Electrical load

Abstract

Existing acoustic energy harvesters are typically resonant structures operated with matched loads, yielding narrowband, and hence low, energy collection from broadband noise sources. Additionally, existing acoustic energy harvesters tend to exhibit MEMS-scale sizes, with correspondingly low power collection and outputs. In contrast, this paper presents the combined real and reactive electrical loading of a wide-area harvester which yields efficient broadband harvesting at higher power. Building on the harvester designed and modeled in Part I, this paper develops the reactive loading and its operational amplifier implementation, illuminating along the way several design issues critical to optimal performance and stability. The loading enables an experimental harvester capable of harvesting acoustic energy with an efficiency of 0.3%–3% over the frequency range of 50–500 Hz. The harvester is demonstrated in a real-world scenario, collecting approximately 2.3 μJ per aircraft takeoff event in an airport environment. This demonstrates the efficacy of acoustic energy harvesting energy and its potential for powering wireless sensor nodes in real-world noisy environments. While the loading is implemented here with lossy operational amplifier circuits, it is amenable to implementation with efficient power electronics.